#include <iostream>
#include <regex>

bool isIdentifier(const std::string& name) {
  std::regex pattern {R"(([a-zA-Z]|_)([a-zA-Z0-9]|_)*)"};
  return std::regex_match(name, pattern);
}

using namespace std;

int main()
{
    cout<<isIdentifier("alma");
}
